Process of producing paper stock



Patented Feb. 10, 1931 PATENT OFFICE HARRY 1. BASSETT, OF CYNTHIANA,KENTUCKY PROCESS OF PRODUGHTG PAPER STOCK No Drawing. Application filedJune 3,

.This invention relates to the production of paper stock and is, inpart, a continuation of my copending application, processes of producingpaper stock, filed July 25, 1921, Serial An object of the presentinvention is the production of paper stock which is hydrolyzed to suchan extent that suflicient vegetable mucilage or hydrated cellulose willbe formed to properly cement the fibre together without resorting toprolonged or extensive beating. i

In the manufacture of paper stock from cotton linters, or other fibrousmaterial, it

has heretofore been necessary to properly condition the fibres forhydrolysis. The physical construction of cotton fibres varies to such anextent that any attempt to hydrolyze them by processes heretofore usedwithout preliminary beating will result in the complete hydrolyzation ofthe more tender fibres before the more resistant ones havebeen'afiected. It has heretofore been necessary to resort to prolongedand extensive beating prior to hydrolyzing in order to break 'up themore resistant fibres.

In the present invention, I have found that the fibres may be properlyprepared by a slight beating operation while the fibres are in a weakacid condition and I attain this result by treating the fibres with aweak acid solution or a solution of an acid salt during the beatingoperation. In the combined beat ing and acid treatment, I preferablyemploy 3 a mineral acid such as sulfuric acid or a mineral acid salt ofapproximately .05 per cent strength to l per cent strength by weight 7at a selected temperature above 20 C., and not materially in excess of100 C. and then 40 treat the material with a solution of an alkali.

The alkali treatment may be preceded by the' 1925. Serial No. 84,738.

preferably a weak solution of sodium hydroxide of less than 2 per centstrength, a soda pulp is-formed. When this material is formed, it issubsequently submitted to a combined acid and beating treatment with asolution of an acid or an acid salt, such as sulfuric acid ofapproximately .05 per cent to 1 per cent strength at a selectedtemperature above 20 0., but not materially in excess of 100 0., an acidpulp is formed, the cellue lose molecules of the fibre being hydrolized.

I have found that when the fibres are submitted to a slight beatingoperation when in an acid condition, as by treating with the acid in themanner set forth, during the beat- 5 ing operation a product is obtainedwhich will completely pass through the screen. On the other hand, if thesame percentage of acid and alkali is employed and the fibres merelysubmitted to a slight beating operation when 7 in an alkali condition,the resulting product will not pass through the screen. The productobtained by submitting the fibres to a slight beating operation when inacid-condition, may be employed either alone or in admixture withsulfite pulp or similar pulp in the manufacture of paper.

In a typical embodiment of the process wherein the preliminary acid andbeating treatment is employed, cotton linters or other 30 cellulosefibre is placed in a heater and treated during the beating operation,with a weak solution of an acid, preferably a mineral acid, such assulfuric acid, or an acid salt of approximately from .05 per cent.strength to 5 1 per cent. strength by weight at a selected temperatureabove 20 (3., and not materially in excess of 100 (3., from one-half tofour hours. As stated, it is essential that the material be in an acidcondition when submitted to the-beating operation and I preferablyem loya combined acid and beating treatment m which the acid solution is addedto the material in a beater. The material is then washed to remove theacid and treated with a solution of an alkali, preferably a solution ofsodium hydroxid of less than 2 per cent. strength to form solubleorganic salts. It is then washed to remove the soluble organic salts. Ihave found that if this soda pulp is then treated with an acid or anacid salt, preferably sulfuric acid, or sodium acid sulfate of from .05to 1 per cent. strength at a temperature of from 20 to 100 C., an acidpulp is formed in which the fibres have been sufficiently hydrolyzed toproduce suificient vegetable mucilage to cement them together.

In this acid treatment, the cellulose molecules are hydrolyzed and avegetable mucilage is formed. The material may be employed in themanufacture of paper either along or in admixture with paper stockformed by the usual sulfite process, or other paper stock of likecharacter.

The process may be performed by first treating the cellulose fibres witha weak solution of an alkali, preferably a weak solution of sodiumhydroxide of less than 2 per cent. strength and then performing thecombined acid and beating treatment above described.

Where a soda pulp is desired, the subsequent acid step is elminated, andthe fibres submitted to the first acid treatment and the alkalitreatment.

The character of the material obtained may, in either case, bedetermined by testing the viscosity of solutions formed by dissolving asmall quantity of this cellulose or cellulose compound formed therefromin a suitable solvent such as cupra-ammonia, or the like. In eithercase, the character of the resulting material may be controlled byvariation of the acid strength, the temperature, or time of treatment.By employing variations in acid strength, temperature and time oftreatment, materials may be obtained capable of forming cellulosecontaining solutions of a desired viscosity. If, for example, acid of.05 per cent. strength is used, the resulting material will be capableof forming a cellulose containing solution which will have a higherviscosity than if acid of higher 'strength within the range of fromapproximately .05 per cent. to 1 per cent. is used. Similarly, in thetreatment of fibre with weak acid of a predetermined strength, theviscosity of a solution formed from the resulting material will behigher if the hydrolysis is carried out at 20 C., than if carried out ata higher temperature within the range of from 20 C. to 100 C. With theacid strength and the temperature remaining constant, a material capableof forming solutions of higher viscosity will be obtained by shorteningthe time of treatment.

After the material has been treated with sodium hydroxid or otheralkali, either with or without the preliminary combined acid and beatingtreatment, materials capable of forming cellulose containing solutionsof a relatively high degree of viscosity can be obtained by the use ofan acid solution of a strength near the lower range of acid strengthsset forth at a temperature somewhat below 80 C. I can obtain materialscapable of forming solutions of a fairly high viscosity by conductingthe hydrolysis at a temperature as low as 20 C., and I have obtained thebestresults in producing solutions of high viscosity by the use of acidof about .05 per cent. acid strength at a temperature of about 80 C. Inproducing materials capable of forming solutions of medium viscosity,the soda pulp is hydrolyzed at a temperature of about 90 (3., using acidof a desired strength approximately from .05 to 1 per cent. of acid butas I prefer to hydrolyze at about 80 C. where a solution of lowviscosity is not required, I prefer, in the treatment of materials foruse in forming solutions of medium or relatively low viscosity to employan acid of from approximately .25 per cent. to 1 per cent. strength at atemperature of about 80 C.

In producing solutions of low viscosity, I use acid of about 1 per cent.strength at a temperature of about 100 C.

From my experiments, it appears that the character of the'material to beobtained may be regulated by an acid treatment subsequent to the alkalitreatment with or without a preliminary combined acid and beatingtreatment, or may be regulated by a preliminary acid treatment with orwithout subsequent acid treatment. Of the factors affecting thecharacter of the material produced, the temperature at which thehydrolysis is conducted is more important, and a considerable range ofdifference in the character of the material and the viscosity ofsolutions formed therefrom is obtainable by merely varying thetemperature at which the acid treatment is carried out, but to obtainthe widest range of difierence in the character of material, and theviscosity of solutions formed therefrom, it will be understood that thetemperature within the limits set forth, the time of treatment, and thestrength of the acid within the limits set forth must be varied inaccordance with the invention, the viscosity being correspondinglyincreased as weaker acid within the range of from .05 to 1 per cent.strength is used, as a lower temperature within the range of from 20 C.to 100 C. is employed, and as the time of treatment is shortened.

The degree of strength of the solution of alkali employed does notappear to affect the viscosity of the cellulose containing solution. Iprefer, however, to employ a solution of from 1 to 2.5 per cent.strength of a basic compound of an alkali or alkaline earth metal,preferably sodium hydroxid. It will, of course, be understood that thesubsequent acid treatment will be continued until the gummy constituentsof the cellulose fibre are completely hydrolyzed as can readily bedetermined by theexamination of a test sample and that in the treatmentof fibre of a uniform grade, a duration of treatment found byexamination tobe satisfactory will be followed. Similarly, the alkalitreatment will be continued until the hydrolyzed gums are whollyconverted into soluble bodies and the washing operations con tinueduntil the soluble bodies are removed.

If the purified fibre is to be bleached, I may employ any of the wellknown bleaching treatments, but I prefer to employ a solution of calciumhypochlorite of about .5 per cent. strength.

While I have described in detail the preferred practice of my process,it is to be understood that the details of procedure, and proportions ofingredients may be widely varied, and that known chemical equivalents vmay be employed in place of the materials mentioned without departingfrom the spirit of the invention or the scope of the subjoined c aims.

I claim:

1. The process of making paper stock which comprises submitting cottonlinters or like fibrous material to a combined slight beating and acidtreatment with a weak acid solution containing a selected per cent. ofacid between .05 and 1 per cent. strength at a temperature between 20and 100 C. to effect partial hydrolysis of the material, and treatingthe material with a weak alkali solution after the combined acid andbeating treatment.

2. The process of making paper stock which comprises submitting cottonlinters or like fibrous material to a combined slight beating and acidtreatment with a weak acid solution containing a selected per cent. ofacid between .05 and 1 per cent. strength at a temperature ofsubstantially C. to efiect partial hydrolysis of the material andtreating the material with a weak alkali solution after the acidtreatment.

3. The process of making paper stock which comprises submitting cottonlinters or like fibrous material to a combined slight heating and acidtreatment with a weak acid solution containing a selected percentage ofacid of less than 1 per cent. strength at a temperacomprises submittingcotton linters or like fibrous material to a combined slight beating andacid treatment with a weak acid solution to efi'ect partial hydrolysisof the material, washing, treating the resulting material with a weakalkali solution, washing, and treating the material with an acidsolution containing a selected quantity of acid of less than 1 per cent.strength at a temperature between 20 and C.

6. The process of makingpaper stockwhich comprises treating cottonlinters or like fibrous material with a weak alkali solution, andsubmitting the material to a combined slight beating and acid treatmentwith a weak acid solution containing a selected per cent. of acidbetween .05 and 1 per cent. strength at a temperature between 20 and 100C., after the alkali treatment.

7. The process of making paper stock which comprises treating cottonlinters or like fibrous material with a weak alkali solution, andsubmitting the material to a combined slight beating and acid treatmentwith a weak acid solution containing a selected per cent. of acidbetween .05 and 1 per cent. strength at a temperature of substantially80 C., after the alkali treatment.

8. The process of making paper stock which comprises treating cottonlinters or like fibrous material with a weak alkali solution,

and submitting the material to a combined slight beating and acidtreatment with a weak acid solution containing a selected per cent. ofacid of less than 1 per cent. strength at a temperature between 20 and100 (1, after the alkali treatment.

In testimony wherof, I afiix my signature.

HARRY P. BASSETT.

ture between 20 and 100 C. to efiect partial hydrolysis of the material,and treating the resulting material with a weak alkali solutionafter theacid treatment.

4. The process of making paper stock which comprises submitting cottonlinters or like fibrous material to a combined slight beating and acidtreatment with a Weak acid solution to effect partial hydrolysis of thematerial, washing, treating the material with a weak alkali solution,washing, and treating the material with a weak acid solution containinga selected per cent. of acid between .05 and 1 per cent. strength at atemperature of substantially 80 C.

5. The process of making paper stock which

